40. There are plenty of videos of people hitting things.

The dead kids at Sandy Hook are more than enough proof that firing this way hits the intended target.

If you look at a lot of these videos, many of them are people trying this for the first time, while others are intended to show how quickly one can learn to do it, as a demonstration, followed by video of someone doing so for the first time.

Many of the other videos are of the 'this is my new AR 15, and my first time firing it, including bump firing'.

It is something that seems to be a subject people want to memorialize on their first time doing this.

I posted a random sampling. If you want to see more, do your own search.

These dweebs as you call it are a significant part of the gun culture and of gun owners. You can't dismiss them from being part of the problem that is the concern of gun control.

There are a variety of features which are directly related to the ease of spray fire. Do your own homework on it; if you are unsuccessful, get back to me by email, and I will provide you some sources.

Barrel shrouds are another feature which facilitate bump firing / spray firing, due to the barrel heat generated by that speed of fire.

It is a problem specifically with semi auto assault style weapons. But if you have video of other firearms that can fire without interruption until the magazine is exhausted, please post them.

But the bottom line is that spray fire / bump fire is an issue, a problem, something that needs solution for the problem stated above:
the problem is rapid fire that results in more victims per incident, more wounds per victim per shooting.